Some plant essential oils have long been known to possess properties that can be employed as food or flavoring, and for medicinal and industrial purposes. Different plant species provide different oils. For example, peppermint for the peppermint plant's leaves which provides flavoring is sometimes used as an aid for digestive issues. And clove oil is extracted from flowers and used for flavoring, scent, and various historical medicinal purposes. Eucalyptus oil, produced from the leaves of Eucalyptus globulus is used in many cleaning solutions and as an antiseptic.
As another example, Monarda fistulosa and many other plants belonging to the true mint family i.e. labiate, have been a source of geraniol, thymol and carvacrol essential oils. Geraniol is used in perfumes. Thymol is used in mouthwash as an antiseptic and has been shown to have antifungal activity, as well. It is known that Carvacrol may also be used as an antimicrobial, antifungal and as a flavoring. Thymoquinone and Thymohydroquinone are also essential oils present in the Monarda fistulosa plant. Thymoquinone has recently been discovered to have specific effects on some mammalian cancers and is a phytochemical found in the plant Nigella sativa and several other plants. It is an antioxidant and has been shown to effect or decrease damage caused by heart, liver and kidney diseases in animal studies. Thymoquinone is an angiogenesis inhibitor and appears to have analgesic and anti-convulsant effect. Tests have shown thyrnoquinone kills pancreatic cancer cells and may have promise related to controlling certain kinds of epileptic seizures.
Although it would seem likely that every plant of a species would have a similar oil content profile, it has been found instead that different races of a plant species may provide different ratios of the essential oils they produce. There are many theories as to the reasons for these differences which include response to climate, moisture levels, nutrient levels, evolution due to these pressures, etc.
Many plants are indigenous to a particular geographic area and/or climate. Historically, those who sought plant oils would gather many plants from their natural habitat. Some plants containing desirable oil have been cultivated for research purposes related to the oil. However, commercial use of Monarda to date includes propagation for seeds to add color to natural prairie and wildflower seed mixes, or selected Sweet Monarda may be grown to produce geraniol used in perfumes.
Cultivation for research or seed purposes may include transfer of the plants from their native growth area to a different geography, climate or soil type or a combination of these. Natural travel of seeds from one area to another may also result in new habitats for a given plant wherein the new habitat may include differing climate, soil, or pests from those in the original habitat. It has been noted that such transfer may result not only in different physical characteristics of the plant in response to the environmental differences, but that these changes may, in turn, result in different ratios of the oils produced by the plant.
Monarda is a genus consisting of at least about 16 species. The plants are erect, herbaceous, annual or perennial, in the family Lamiaceae and are native to North America. The plants typically range in height from 1 to 3 feet (0.2 to 0.9 m), the plants have an equal spread, with slender and long-tapering (lanceolate) leaves. The leaves, when crushed, exude a spicy, highly fragrant oil. Common names include bee balm, horsemint, and bergamot, among others. When the term “Monarda” is used herein it is understood that it includes plants known by these names, as well, provided the plant meets the characteristics of the Monarda genus.
In the case of Monarda fistulosa, several studies provide information pertinent to the present invention. In the early 1970's anew chemical race of Monarda fistulosa was discovered in Manitoba Canada and studied. (MARSHALL H, H, and R. W. SCORA.1972. A new chemical race of Monarda fistulosa (Labiatae). Can. J. Bot. 50: 1845-1849.) Monarda fistulosa is widely distributed throughout North America and a plant had been discovered having a different scent than most others. It was dubbed “sweet Monarda” due to the scent which was the only difference discemable without chemical testing. Other Sweet Monarda plants were then found, albeit far more scarce than the dominant type. The Sweet Monarda plants were generally more scarce and did not grow at many of the study's collection sites. Typically, the sweet Monarda plants were collected on light sand and stabilized dunes.
Sweet Monarda was crossed with other Monarda. Then the oils of the crosses and of the Sweet Monarda were studied using chromatography of the leaf oil. The researchers found that oil from the nonsweet Monarda was moderately viscous and was reported clear and colorless whereas oil from Sweet Monarda smelled sweet. Chromatograms showed that oil from the Sweet Monarda included far more geraniol but far less thymol and carvacrol than the non-sweet Monarda plants tested.
Another study completed in 1993 looked at Monarda as a source of certain oils, specifically, geraniol, linalool, thymol and carvacrol. This study also presented the idea that plants of a given species but grown and maintained in different geographical regions may yield different oils. (Mazza, G., F. A. Kiehn, and H. H. Marshall. 1993. Monarda: A source of geraniol, linalool, thymol and carvacrol-rich essential oils. p. 628-631. In: J. Janick and J. E. Simon (eds.), New crops. Wiley, New York.)
When Monarda fistulosa is crossed with M. didyma a vigorous hybrid is produced that yields geraniol, linalool, thymol, carvacrol and other terpenes. However, multiple crosses as conducted by the study resulted in a sterile plant which had to be propagated by division. The study employed a planting rate of 10,000 plants/ha (or 24,000/acre). The study acknowledged that propagation via crown divisions would be easily achieved but, because crown division is cumbersome and inefficient, the study recommended using stem cuttings instead. The cuttings were recommended to be 10-12 cm in length with their bases dipped in rooting compound and then placed in sand in a misting chamber. Roots were reportedly produced in a week using this method and recommended to be transplanted in 14-16 days. Further, weeds were reported as being easily controlled by herbicides such as trifluralin, terbaacil, solan, and paraquat. Post-harvest, hydrodistillation was employed to extract the oils which were then subjected to gas chromatography and mass spectrometry. One of the hybrids showed a high level of geraniol; this hybrid was grown for a short time in southern Alberta, Canada for geraniol production but for an unknown reason, the plants did not survive the second year.
Rust, otherwise known as Puccinia menthe, was reported as the major disease of the sterile Monarda (Mazza, 1993) causing defoliation, stem damage and degeneration of plants. Recommendations for control of rust include application of the herbicide paraquat in early spring. This article also reported variations of essential oil yields between about 0.65 and 1.2 g/100 g of fresh plant material or between about 60-125 kg of oil/ha.
As described earlier, Carvacrol and Thymol have both antiseptic and antimicrobial activities and have been used accordingly. It also appears that one or both may be used as an herbicide of sorts, specifically, a biochemical fungicide for control of moss and liverwort. Geraniol is used most often for its scent in products such as perfumes. Thymoquinone, as mentioned earlier, is indicated as having therapeutic effect in the treatment of some mammalian cancers and other ailments.
In the present invention, it was postulated by the inventors that levels of oil, and perhaps quality of the oil, in the Monarda fistulosa plants may be at least somewhat dependent on planting and growth methods. Finding a dependable means of growing and harvesting oil from Monarda fistulosa in a manner selective for the desired oil would be beneficial. Developing a method that minimized use of herbicides and pesticides was also desirable in order to produce high quality oil unadulterated by chemical use.
For the most part, historically Monarda fistulosa has been cultivated as a seed for wildflower planting purposes rather than for oil production albeit some plants have been selected for geraniol production
Monarda fistulosa is an erect aromatic annual or perennial plant which bears pretty pinkish/lavender flowers. It is often used in wildflower seed mixes and in prairie restoration projects. Previously recommended methods for cultivation of Monarda fistulosa include planting rates of between about 0.25 lbs/acre and 2 lbs/acre, and cutting and or splitting the plants to increase them, timing of harvest, etc. In terms of labor and time costs, the previous methods are not ideal. Further, none of the literature purports to claim these methods increase the average levels of certain components in the oil such as thymol, carvacrol or thymoquinone.
What was needed was a method of producing Monarda fistulosa on a commercial scale and economically to produce an oil comprising relatively high levels of carvacrol, and/or thymoquinone and/or thymohydroquinone. A desirable method of doing so would reduce cultivation expenses and labor while providing a dependable means for a reliable harvest of the multi-use oil and its constituents.
It was therefore one objective of the present invention to determine appropriate seed planting rates and spacing to provide and encourage efficient production of plants bearing oil having higher levels of carvacrol and/or thymoquinone and/or thymohydroquinone.
It was another objective of the present invention to provide a method of growing Monarda fistulosa that would result in least expense for weed and/or rust control while providing high levels of desired essential oil or oils.
It was another objective of the present invention to provide a method for cultivating Monarda fistulosa that reduced the amount of fuel required, specifically by reducing the need for fuel used to apply herbicides, and boiler fuel used in distilling/cooking through unwanted weeds mixed in with the Monarda. 
It was another objective of the present invention to provide a method for planting, cultivating and harvesting Monarda fistulosa that provided an economically viable manner of producing one or more essential oils.
It was a primary objective of the present invention to provide a method of cultivation of Monarda fistulosa that increased consistent results of high quality and relatively high production levels of the desired oil constituents.